Issue #13257 has been updated by Akinori MUSHA.


Is that a use case where you need a method for checking without allocating a singleton class?
As I read it diagonally, it looks like you are always accessing and using the singleton class when an object has one.

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Bug #13257: Symbol#singleton_class should be undef
https://bugs.ruby-lang.org/issues/13257#change-63309

* Author: Satoshi TAGOMORI
* Status: Feedback
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.4.0p0 (2016-12-24 revision 57164) [x86_64-darwin15]
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
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Objects of some classes doesn't have singleton classes (e.g., Symbol, Integer, Float...).
Symbol#singleton_class raises TypeError.

But Symbol#respond_to?(:singleton_class) returns true, and we cannot know when #singleton_class returns a valid class or raise errors in any way (except for calling it).

I think that such #singleton_class methods should be undef.



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